In read-only optical disc media such as ROM (Read Only Memory) type CD (Compact Disc), DVD (Digital Versatile Disc), and BD (Blu-ray disc: Registered Trademark), a lead-in area, a main data area, and a lead-out area are formed from the inner circumference side toward the outer circumference side on the optical disc.
Information data of music, images, games, application programs, etc. is recorded in the main data area according to a predetermined recording modulation method. Further, in the lead-in area, various kinds of management information such as information for reproduction management of information data recorded in the main data area and physical information of the disc are recorded.
For example, these read-only optical disc media are utilized as means for providing content by many content holders because of low production cost from their excellent mass productivity.
By taking DVDs (DVD-ROMs) as an example, the manufacturing process of read-only optical disc media is roughly divided into a mastering step of fabricating a master of optical discs with a laser beam, a molding and film-forming step of fabricating many disc substrates using a stamper fabricated from the optical disc master and forming films on the disc substrates, and a bonding step of bonding paired two 0.6-mm-thick optical discs with an adhesive having a predetermined thickness to form 1.2-mm-thick DVD disc media.
At the molding and film-forming step, a concavo-convex pattern formed on the stamper is transferred onto the disc substrates in mass-production using the stamper. That is, recording data rows (pit rows) of embossed pits/lands as a concavo-concave shaped pattern are formed in a part as an information recording surface, and the recording data rows are formed in spiraled or coaxial recording tracks. On the information recording surface on which the pits/lands have been formed, the concavo-concave shape is coated with a metal alloy reflecting film.
After the disc is completed, a laser beam applied by a reproduction device is reflected by the reflecting film in the pits/lands part.